Refrigerant for refrigerating processes in which the refrigerant has to be compressed



Patented Sept. 17, 1935 UNITED STATES REFRIGERANT FOR REFRIGERATING PROCESSES IN WHICH THE REFRIGER- ANT HAS TO BE COMPRESSED August Guyer, Zurich, Switzerland, assignor to the firm Escher Wyss Maschinenfabriken, Aktiengesellschaft, Zurich, Switzerland No Drawing. Application March 27, 1933, Serial No. 663,104. In Switzerland April 5,1932

4 Claims.

Ammonia, sulphur dioxide, and carbon dioxide are preferably used as refrigerants for refrigerating cycles or processes in which the refrigerant has to be compressed. The use of hydrocarbon compounds for the same purpose has also been proposed and, as some of the compounds in question are not combustible and at the same time, have suitable boiling points they have actually been used in practice, to a certain extent. The boiling point of the refrigerant used plays every important part, especially in refrigerating plants with centrifugal compressors, such as have come more and more into use in recenttimes for refrigerating on a large scale. It is desirable for the temperature at which the refrigerant emplayed boils under atmospheric pressure to lie between the lowest and the highest temperature occurring in the process, because, when such is the case, the evaporator pressure is less than atmospheric pressure, while the liquefier pressure, on the other hand, is higher than the pressure of the atmosphere. This considerably facilitates the packing of the outwardly extending parts of the rotor of the centrifugal compressor, for it is then possible, for instance, so to connect the stufilng boxes of the compressor, by means of a pipe, or duct, that the medium which leaks from the stuffing box which is under a super-atmospheric pressure acts as a sealing medium for the stufling box which is under a sub-atmospheric pressure. In this way, any entrance of air into the apparatus and any escape of refrigerant medium into the atmosphere can almost be completely prevented in practice, this being a matter of great importance from the standpoint of safe working.

The refrigerant to be compressed in a centrifug'al compressor must, however, possess also as high a density as possible, or, which amounts to the same thing, as high a molecular weight as possible; the more this condition is satisfied the fewer the number of compressor stages required for a given refrigerating capacity and the easier it becomes to construct a simple and eflicient compressor for the purpose in view. 7

The simultaneous satisfaction of the requirement of high molecular weight and the requirement of a favourably situated boiling point presents considerable difficulties inasmuch as just those substances which are of high molecular weight mostly have, as is well known, high boiling points also. The requirements mentioned will, however, be suii ciently satisfied if, according to the present invention, vinyl bromide (CHzzCHBr) or its higher homologues alphaand beta-bromopropylene, or alphaand beta-chloropropylene,

be used as refrigerants for refrigerating processes in which the refrigerant is to be compressed.

That the substances which it is proposed to use according to the present invention have not previously been suggested as refrigerants for refrigerating processes in which the refrigerant is compressed may be due to the known fact that they have a great tendency to polymerize and also, under certain circumstances, may decompose. I 10 have however found as the result of experiment that such decomposition only occurs at temperatures which are higher than the highest temperature attained in refrigerating processes of the kind herein referred to. I have, further, found that polymerization does not take place in a closed apparatus which is impenetrable to light rays. Even in cases, however, in which it is not possible completelyto exclude light, a refrigerant according to this invention can be stabilized by the addition of substances, such, for example, as iodine, which protect it from the action of light and prevent polymerization.

If, for instance vinyl bromide .be used in a. refrigerating plant of large capacity with a centrifugal compressor, a comparatively small number of stages may be used, on account of the great density of this substance. In addition to this, the favourably situated boiling point of vinyl bromide, namely 16 C. at atmospheric'30 pressure, ensures that the evaporator pressure will lie not much below 1 atmosphere absolute (at 0 C. it amounts to 0.6 atmosphere absolute) while the pressure of the liquefler will lie somewhat above 1 atmosphere absolute (at 25 C. it amounts to 1.45 atmospheres absolute and at 30 C. it amounts to 1.7 atmospheres absolute). Alpha-bromopropylene, the boiling point of which, at atmospheric pressure, is 595 C., may conveniently be used, if no lower temperature 40 than 60 C. occurs in the liquefler, while betabromopropylene, the boiling point of which, at atmospheric pressure, is from 47 to 48 C., is suitable when the liquefier temperature lies above 4 48 C. The boiling points of alpha-chloro propylene (36 C. at atmospheric pressure) and of betachloropropylene 23 C. at atmospheric pressure) both of which also have a high molecular weight, are just as favourably situated as the boil- 50 ing point of vinyl bromide. As they, together with vinyl bromide and its higher homologues, are moreover connected by the vinyl group common to all these substances, all of them are closely.- related;

pressing and expanding bromopropylene as refrigerant. I

4. The refrigeration method comprising circu lating a bromide of one of the lower members of the vinyl group as refrigerant through oompression and expansion steps in the presence of iodine as a stabilizer to prevent polymerization.

AUGUST GUYER. 

